Improving upon existing B cell lymphoma therapies requires elucidation of the mechanisms of disease etiology. We have developed a novel murine model of B cell lymphoma in mice lacking the inositol phosphatases PTEN and SHIP specifically in B cells (bPTEN/SHIP-/-). bPTEN/SHIP-/- mice develop a lethal B cell lymphoma that resembles human activated B-NHL, with 100% penetrance within 1 year of life. In this proposal, we aim to utilize bPTEN/SHIP-/- mice in order to determine: (1) the cellular and molecular characteristics of bPTEN/SHIP-/- lymphoma;(2) whether B-NHL development requires antigen (Ag)-mediated clonal selection;(3) if BAFF is a critical promoter of B-NHL;and (4) the cellular and molecular differences between lymphoid vs. metastatic lymphoma cells. To determine the nature of the lymphoma that develops in bPTEN/SHIP-/- mice, we will examine cell surface phenotype and ability to grow in culture without stimulation or survival factors, and perform CFU assays and S. blot analyses for clonality. We will perform structure-function analyses of PTEN and SHIP in reconstituted bPTEN/SHIP-/- B cells in order to determine how loss of PTEN and SHIP each contribute to B-NHL development. To determine if B-NHL development/progression requires recognition of self-Ag, we will restrict the repertoire of bPTEN/SHIP-/- B cells away from self-reactivity by enforced expression of a defined BCR or, in parallel, introduce non-self Ags. We will neutralize BAFF in order to test the hypothesis that BAFF promotes the expansion of B-NHL. To test the hypothesis that lymphoma cells infiltrating non-lymphoid organs acquire enhanced pathogenicity, we will use adoptive transfer of bPTEN/SHIP-/- B cells from non-lymphoid organs into TCR[unreadable]d-/- recipients, and use gene chip arrays to identify genes that are differentially regulated between lymphoid and metastatic B cells. Taken together, these proposed studies utilize a novel system, and are timely and necessary for the further understanding of the development of B-NHL as well as mechanisms by which current therapies maybe improved upon and new treatments developed. Despite successes in the development and application of B cell-specific therapeutics for B-Non-Hodgkin's lymphoma (B-NHL), several types of B-NHL remain virtually untreatable. bPTEN/SHIP-/- mice represent a novel system in which to elucidate the molecular mechanisms of lymphoma progression and metastasis. The ultimate goal of this proposal is to utilize what is discovered for the rational design of next-generation therapeutics against B-NHL.